Pixel unit and method for manufacturing the same, display panel, and display apparatus

ABSTRACT

The present invention discloses a pixel unit and a method for manufacturing the same, a display panel, and a display apparatus. A pixel unit comprises a first electrode, a pixel defining layer, a light emitting layer and a second electrode, wherein the second electrode comprises a first portion and a second portion; the pixel defining layer defines a pixel region, the light emitting layer and the first portion of the second electrode are disposed successively within the pixel region, and an upper surface of the first portion of the second electrode is substantially in same plane with an upper surface of the pixel defining layer; and, the second portion of the second electrode is positioned over the first portion and is connected with a second electrode of an adjacent pixel unit. With the technical solutions of the present invention, phenomenon including fractures, abscissions, bubbles and the like due to existence of difference in height in the pixel region will be eliminated, averting adverse influence resulting in failures of the display apparatus.

BACKGROUND

Technical Field

Embodiments of the present invention relate to the field of displaytechnologies, and particularly, to a pixel unit and a method formanufacturing the same, a display panel, and a display apparatus.

Description of the Related Art

Organic Light-Emitting Diode (OLED) device, due to its advantagesincluding fully solid state construction, high brightness, full viewingangle, fast response time, broad working temperature range, flexibledisplaying and the like, becomes currently a younger generation displaytechnology which is highly competitive and has a development prospect.

FIG. 1 shows a conventional process of manufacturing an OLED displayapparatus. Firstly, array 102 of thin-film transistors (TFT) ismanufactured on a flexible substrate 101, in which ITO pixel electrodesare separated by a pixel defining layer (PDL) 103 to define a pixelregion; then, material 104 for light emitting layer and material 105 fornegative electrode are deposited within the pixel region; and finally,subsequent processes are performed, to finish manufacture of the OLEDdisplay apparatus. Generally, material for light emitting layercomprises a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), anOrganic Layer, an Electron Transport Layer (ETL), and an ElectronInjection Layer (EIL). In conventional process, the Hole Injection Layer(HIL), the Hole Transport Layer (HTL), the Electron Transport Layer(ETL), and the Electron Injection Layer (EIL), etc. are deposited mainlyby means of using an open-type mask, material for the Organic Layer R,G, B is deposited by means of using a fine metal mask (FMM), and,material for negative electrode is usually deposited by means of usingan open-type mask. In the subsequent processes, flexible packaging,i.e., thin film encapsulation (TEF), Dam &Fill, or adhesive+barrierfilm, is performed.

Material for the pixel defining layer is usually made of adhesive andhas a thickness at micrometer-scale, while thicknesses of the materialsfor the light emitting layer and for the negative electrode depositedare of the order of magnitude of hundreds of nanometers. As a result,there is difference in height between material for the pixel defininglayer and material for the light emitting layer as well as material forthe negative electrode thereover. For a flexible OLED display apparatus,when the OLED display apparatus is bent, such difference in heightbetween the pixel defining layer and the negative electrode likelycauses phenomenon including fractures of the negative electrode orabscissions of the negative electrode from the pixel defining layer tooccur at a stress concentration zone. Secondly, for flexible packaging,such as barrier film, Dam &Fill, and TFE, bubbles extremely likely occurat a position where there is difference in height between the pixeldefining layer and the negative electrode, adversely affecting thepackage effect. These problems greatly adversely affect display effectof the display apparatus, and even cause failures of the displayapparatus.

SUMMARY

According to a first aspect of the present invention, there is provideda pixel unit comprising a first electrode, a pixel defining layer, alight emitting layer and a second electrode, wherein the secondelectrode comprises a first portion and a second portion; the pixeldefining layer defines a pixel region, the light emitting layer and thefirst portion of the second electrode are disposed successively withinthe pixel region, and an upper surface of the first portion of thesecond electrode is substantially in same plane with an upper surface ofthe pixel defining layer; and, the second portion of the secondelectrode is positioned over the first portion and is connected with asecond electrode of an adjacent pixel unit.

According to a second aspect of the present invention, there is provideda display panel comprising the abovementioned pixel unit.

According to a third aspect of the present invention, there is provideda display apparatus comprising the abovementioned display panel.

According to a fourth aspect of the present invention, there is provideda method for manufacturing a pixel unit, the method comprising:

forming a first electrode;

forming a pixel defining layer, and patterning the pixel defining layerto define a pixel region;

forming a light emitting layer within the pixel region;

forming a first portion of a second electrode on the light emittinglayer such that an upper surface of the first portion of the secondelectrode is substantially in same plane with an upper surface of thepixel defining layer;

forming a second portion of the second electrode on the first portion ofthe second electrode, wherein the second portion of the second electrodeis connected with a second electrode of an adjacent pixel unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a plurality of pixel units in an OLEDdisplay apparatus made by conventional process in the prior art;

FIG. 2 is a schematic view of a pixel unit according to an embodiment ofthe present invention;

FIG. 3 is a schematic view of a plurality of pixel units, manufacturedby an open-type mask, according to an embodiment of the presentinvention;

FIG. 4 is a flow diagram of a method for manufacturing a pixel unitaccording to an embodiment of the present invention; and

FIGS. 5(A)-5(E) are flow diagrams of processes of manufacturing a pixelunit according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to provide a more clear understanding of objects, techniquesolutions and advantages of the present invention, embodiments of thepresent invention will be further described hereinafter in detail inconjunction with these embodiments and with reference to the attacheddrawings.

For easy explanations, lots of details are presented in the followingdescription in order to provide a complete understanding of thesedisclosed embodiments. However, obviously, one or more embodiments canbe implemented without these details. In other cases, well-knownstructures and devices are simplified for clear purposes.

In accordance with a general concept of the present invention, thereprovides a pixel unit comprising a first electrode, a pixel defininglayer, a light emitting layer and a second electrode, wherein the secondelectrode comprises a first portion and a second portion; the pixeldefining layer defines a pixel region, the light emitting layer and thefirst portion of the second electrode are disposed successively withinthe pixel region, and an upper surface of the first portion of thesecond electrode is substantially in same plane with an upper surface ofthe pixel defining layer; and, the second portion of the secondelectrode is positioned over the first portion and is connected with asecond electrode of an adjacent pixel unit. Meanwhile, there alsoprovides a method for manufacturing the abovementioned pixel unit, adisplay panel comprising the abovementioned pixel unit, and a displayapparatus comprising the abovementioned display panel.

FIG. 2 is a schematic view of a pixel unit according to an embodiment ofthe present invention. Referring to FIG. 2, the pixel unit comprises asubstrate 200, a first electrode 201, a pixel defining layer 202, alight emitting layer 203 and a second electrode 204, wherein the secondelectrode 204 comprises a first portion 2041 and a second portion 2042;the pixel defining layer 202 defines a pixel region, the light emittinglayer 203 and the first portion 2041 of the second electrode 204 aredisposed successively within the pixel region, and an upper surface ofthe first portion 2041 of the second electrode 204 is substantially insame plane with an upper surface of the pixel defining layer; and, thesecond portion 2042 of the second electrode 204 is positioned over thefirst portion 2041 and is connected with a second electrode of anotherpixel unit.

It can be seen from FIG. 2, the upper surface of the first portion 2041of the second electrode 204 is substantially in same plane with theupper surface of the pixel defining layer. Accordingly, there issubstantially no difference in height existing between the first portion2041 of the second electrode 204, as common electrode, and the pixeldefining layer 202, so that the second portion 2042 of the secondelectrode 204 is substantially flat. As a result, when the display panelformed by the pixel unit is bent, phenomenon, which adversely affectsencapsulation effect, including fractures or bubbles, will not occur. Asbeing known for those skilled in the art, due to technical restrictions,certain amount of difference in height may appear between the firstportion 2041 of the second electrode 204 and the pixel defining layer202, however, if the amount of difference in height is restricted withina certain range, for example, from −200 nm to 200 nm. Since the amountof difference in height is very small, the effect of such difference inheight on a flatness of the second portion 2042 of the second electrode204 is almost negligible. As a result, in a practical manufacturingprocess, the object of the present invention can be achieved, so long asthe amount of difference in height between the first portion 2041 of thesecond electrode 204 and the pixel defining layer is within apermissible error range, in order words, so long as the upper surface ofthe first portion 2041 of the second electrode 204 is substantially insame plane with the upper surface of the pixel defining layer.

Optionally, the first electrode 201 is located below both the pixeldefining layer 202 and the light emitting layer 203, and is connectedwith a first electrode 201 of another pixel unit to form commonelectrode, as shown in FIG. 2. In other embodiments, the first electrode201 is located only below the light emitting layer 203 and certain gapsare provided among the first electrodes 201 of different pixel units.

Optionally, the first electrode 201 may be positive electrode ornegative electrode, and preferably is positive electrode. If the firstelectrode 201 is positive electrode, material for the first electrode201 may include high work content transparent conductive material orsemitransparent conductive material, for example, ITO, Ag, NiO, Al orgraphene. If the first electrode 201 is negative electrode, preferably,material for the first electrode 201 may include low work content metalsor combinations thereof, for example, one or any combinations of Al, Mg,Ca, Ba, Na, Li, K and Ag.

Optionally, the first electrode 201 may have a shape of parallelogram orellipse. Here, parallelogram may include rectangle, square or rhomb. Inpractical applications, the first electrode 201 may also have any othershape, e.g., quadrilateral of arbitrary structure, in accordance withproduction requirements.

It should be noted that, position of formation, material and shape, etc.of the first electrode 201 are not limited to those recited in the aboveembodiments, as long as it can achieve the functions of a positiveelectrode or a negative electrode of the pixel unit and is applicable inembodiments of the present invention.

Optionally, the pixel defining layer 202 may be made of inorganicmaterial, e.g., SiO₂, SiNx and the like. Or else, it may be made oforganic material, e.g., photoresist and the like.

Optionally, the pixel defining layer 202 is formed on the firstelectrode 201 and has an annular structure in which the pixel region isdefined, and, both the light emitting layer 203 and the first portion2041 of the second electrode 204 are formed within the pixel region suchthat the pixel defining layer 202 is disposed around them. The substrate200 may be a glass substrate, or an array substrate formed with TFTarray circuit.

Optionally, the light emitting layer 203 comprises a hole injectionlayer, a hole transport layer, an organic layer, a hole stop layer, anelectron stop layer, an electron transport layer, and an electroninjection layer; or it comprises an organic layer and/or one or anycombination of these other layers.

The second electrode 204 is formed on the light emitting layer 203.

Optionally, the second electrode 204 may be positive electrode ornegative electrode, and preferably is negative electrode. If the secondelectrode 204 is negative electrode, material for the second electrode204 may include low work content metals or combinations thereof, forexample, one or any combination of Al, Mg, Ca, Ba, Na, Li, K and Ag. Ifthe second electrode 204 is positive electrode, material for the secondelectrode 204 may include high work content transparent conductivematerial or semitransparent conductive material, for example, ITO, Ag,NiO, Al or graphene.

Optionally, the first portion 2041 of the second electrode 204 is usedto fill and level up difference in height between the pixel defininglayer 202 and the light emitting layer 203, such that the upper surfaceof the first portion 2041 is substantially in same plane with the uppersurface of the pixel defining layer 202. In other words, a totalthickness of the light emitting layer 203 and the first portion 2041 ofthe second electrode 204 substantially equals to a thickness of thepixel defining layer 202. Optionally, the second portion 2042 of thesecond electrode 204 is formed above not only the first portion 2041 ofthe second electrode 204 but also the pixel defining layer 202. Sincethe upper surface of the first portion 2041 of the second electrode 204is substantially in same plane with the upper surface of the pixeldefining layer 202, the second portion 2042 of the second electrode 204may be evenly disposed on the upper surfaces of the first portion 2041of the second electrode 204 and of the pixel defining layer 202, to forma portion of common electrode connected with another pixel unit, asshown in FIG. 3.

Optionally, the second portion 2042 of the second electrode 204 isformed on the upper surface of part of the pixel defining layer 202 orof the entire pixel defining layer 202. It mainly depends on a processfor manufacturing the second portion 2042 of the second electrode 204.If a slit-type fine metal mask (FMM slit Mask) is employed tomanufacture the second portion 2042 of the second electrode 204, thesecond portion 2042 of the second electrode 204 only covers a portion ofthe pixel defining layer 202, because it is connected with a secondelectrode of an adjacent pixel unit in a fore-and-aft direction but,together with an adjacent pixel unit in a left and right direction,forms a gap. If an open-type mask process is employed to manufacture thesecond portion 2042 of the second electrode 204, the second portion 2042of the second electrode 204 covers whole upper surface of the pixeldefining layer, because it is connected with all the second electrodesof adjacent pixel units around the second electrode. FIG. 3 is aschematic view of a plurality of pixel units manufactured by means of anopen-type mask process. It can be seen from FIG. 3 that, the secondportions 2042 of the second electrodes 204 of the plurality of pixelunits are substantially evenly connected with one another, eliminatingfracture phenomenon occurring in the conventional process.

In embodiments of the present invention, the first electrode 201 ispreferably positive electrode while the second electrode 204 ispreferably negative electrode. This is because, when the secondelectrode 204 is negative electrode, material for the second electrode204 may include low work content metals or combinations thereof, forexample, one or any combinations of Al, Mg, Ca, Ba, Na, Li, K and Ag.The abovementioned materials are suitable for manufacturing by means ofa block-type fine metal mask vapor deposition. Accordingly, theblock-type fine metal mask vapor deposition may be preferably employedin the manufacture of the first portion 2041 of the second electrode204.

In embodiments of the present invention, the block-type fine metal maskvapor deposition is suitable for the manufacture of the first portion2041 of the second electrode 204, this is because the first portion 2041of the second electrode 204 is required to be formed within a pixelregion defined by the pixel defining layer 202, in order to fill andlevel up difference in height between the pixel defining layer 202 andthe light emitting layer 203. Employment of the block-type fine metalmask allows the material for the second electrode to be accuratelymanufactured, by vapor deposition, within the pixel region, withoutinvolving any other process steps and thus reducing process steps.

Optionally, the pixel unit is an OLED unit.

The OLED unit according to embodiments of the present invention issuitable to be used in both a bottom emission type OLED device and a topemission type OLED device, especially, it is suitable to be used in abottom emission type OLED device. This is because that, the secondelectrode (negative electrode) of a conventional top emission typedevice is made of semitransparent metal having a relatively smallerthickness, but in the OLED unit according to embodiments of the presentinvention, the first portion 2041 and the second portion 2042 of thesecond electrode 204 have a relatively greater total thickness, whichmay affect emission of light of the top emission type device,accordingly, it is more suitable to be used in a bottom emission typeOLED device.

An embodiment of the present invention further provides a display panelcomprising a plurality of abovementioned pixel units. Optically, thedisplay panel may be an OLED display panel.

An embodiment of the present invention further provides a displayapparatus comprising abovementioned display panel. Optically, thedisplay apparatus may be an OLED display apparatus.

FIG. 4 is a flow diagram of a method for manufacturing a pixel unitaccording to an embodiment of the present invention. FIGS. 5(A)-5(E) areflow diagrams of processes of manufacturing a pixel unit according to anembodiment of the present invention. Referring to FIGS. 4 and 5(A)-5(E),as an exemplary example, the method for manufacturing a pixel unitcomprising:

a step 401 of forming a first electrode 201;

a step 402 of forming a pixel defining layer 202, and patterning thepixel defining layer 202 to define a pixel region;

a step 403 of forming a light emitting layer 203 within the pixelregion;

a step 404 of forming a first portion 2041 of a second electrode 204 onthe light emitting layer 203 such that an upper surface of the firstportion 2041 of the second electrode 204 is substantially in same planewith an upper surface of the pixel defining layer 202; and

a step 405 of forming a second portion 2042 of the second electrode 204on the first portion 2041 of the second electrode 204, wherein thesecond portion 2042 of the second electrode 204 is connected with asecond electrode of an adjacent pixel unit.

As an exemplary example, in the step 401, optically, the first electrode201 is formed on a glass substrate 200, or on an array substrate 200formed with array circuit, as shown in FIG. 5(A). The substrate 200 maybe flexible substrates made of PET (polyethylene terephthalate), PI(polyimide), PEN (polyethylene naphthalate) and the like.

Optionally, the first electrode 201 may be positive electrode ornegative electrode, and preferably is positive electrode. If the firstelectrode 201 is positive electrode, material for the first electrode201 may include high work content transparent conductive material orsemitransparent conductive material, for example, ITO, Ag, NiO, Al orgraphene. If the first electrode 201 is negative electrode, preferably,material for the first electrode 201 may include low work content metalsor combinations thereof, for example, one or any combinations of Al, Mg,Ca, Ba, Na, Li, K and Ag.

In the step 402, “patterning the pixel defining layer 202” means that aportion of material for the pixel defining layer 202, over the firstelectrode 201 is removed, so that the pixel defining layer 202 has anannular structure. A region surrounded by the annular structure is thepixel region.

Optionally, the pixel defining layer 202 is made of inorganic material,e.g., SiO₂, SiNx and the like. As an exemplary example, the step 402 mayfurther comprise the following sub-steps of:

forming, by means of a chemical vapor deposition, an inorganic materiallayer having a thickness in the range of about 100-400 nm, over thesubstrate 200 formed with the first electrode 201, as shown in FIG.5(B), wherein the inorganic material has a greater thickness than thefirst electrode 201;

spin coating a photoresist on the inorganic material layer, and thenperforming exposure and development, wherein an area of exposure equalsto an area of the pixel region to be formed; and

dry etching the inorganic material layer, to remove the exposed anddeveloped inorganic material layer and removing rest of the photoresist,so as to form the pixel defining layer 202, as shown in FIG. 5(C).

Optionally, the pixel defining layer 202 is made of organic material,e.g., photoresist. As an exemplary example, the step 402 may furthercomprise the following sub-steps of:

coating, by means of slit coating or spin coating, the substrate 200formed with the first electrode 201, with organic photoresist material,to form an organic film having a thickness in the range of about100-2000 nm, wherein the organic photoresist material has a greaterthickness than a height of the first electrode 201; and

exposing and developing the organic photoresist material, wherein anarea of exposure equals to an area of the pixel region to be formed, andwherein over exposure is performed on the photoresist formed on thesurface of the first electrode 201 during the exposing, to completelyremove the photoresist on its upper surface, so as to form the pixeldefining layer 202.

As an exemplary example, referring to FIG. 5(C), in the step 403 offorming the light emitting layer 203, the light emitting layer 203 isformed by means of solution process or vapor deposition process.

Optionally, the step of forming the light emitting layer 203 mayspecifically comprise:

Ink jet printing a hole injection layer (HIL), a hole transport layer(HTL), an organic Layer and the like, respectively, and vapor depositingan electron transport layer (ETL), an electron injection layer (EIL) andthe like, within the pixel region, to finish the manufacture of thelight emitting layer 203.

Referring to FIG. 5(D), in the step 404, “an upper surface of the firstportion 2041 of the second electrode 204 is substantially in same planewith an upper surface of the pixel defining layer 202” means that adifference in height between the first portion 2041 of the secondelectrode 204 and the pixel defining layer 204 is in a range from −200nm to 200 nm.

Optionally, the second electrode 204 may be positive electrode ornegative electrode, and preferably is negative electrode. This isbecause, if the second electrode 204 is negative electrode, material forthe second electrode 204 may include low work content metals orcombinations thereof, for example, one or any combination of Al, Mg, Ca,Ba, Na, Li, K and Ag. The abovementioned materials are suitable formanufacturing by means of a block-type fine metal mask vapor deposition.Accordingly, the block-type fine metal mask vapor deposition may bepreferably employed in the manufacture of the first portion 2041 of thesecond electrode 204. Of course, in the present invention, other processmay be employed in the manufacture of the second electrode 204 as apositive electrode.

Optionally, the first portion 2041 of the second electrode 204 has athickness in the range of 100 nm-1 um.

Optionally, the step 404 may further comprise the following sub-stepsof:

depositing, by means of a block-type fine metal mask, material for thesecond electrode on the light emitting layer 203, to fill and level updifference in height between the pixel defining layer 202 and the lightemitting layer 203, so that the surface of the material for the secondelectrode after the filling and leveling up is substantially in sameplane with the upper surface of the pixel defining layer 202, so as toform the first portion 2041 of the second electrode 204.

In embodiments of the present invention, the block-type fine metal maskvapor deposition is suitable for the manufacture of the first portion2041 of the second electrode 204, this is because the first portion 2041of the second electrode 204 is required to be formed within a pixelregion defined by the pixel defining layer 202, in order to fill andlevel up difference in height between the pixel defining layer 202 andthe light emitting layer 203. Employment of the block-type fine metalmask allows the material for the second electrode to be accuratelymanufactured, by vapor deposition, within the pixel region, withoutinvolving any other process steps and thus reducing process steps.

Optionally, the second electrode 204 may be positive electrode ornegative electrode, and preferably is negative electrode. If the secondelectrode 204 is negative electrode, material for the second electrode204 may include low work content metals or combinations thereof, forexample, one or any combination of Al, Mg, Ca, Ba, Na, Li, K and Ag. Ifthe second electrode 204 is positive electrode, material for the secondelectrode 204 may include high work content transparent conductivematerial or semitransparent conductive material, for example, ITO, Ag,NiO, Al or graphene.

Optionally, referring to FIG. 5(E), the step 405 may further comprisethe following sub-steps of:

continuing to deposit, by means of open-type mask, the material for thesecond electrode, to form a second portion 2042 of the second electrode204; and

covering whole surface of the substrate 200 with the material for thesecond electrode that has been deposited by means of open-type mask. Inother words, both the second portion 2042 of the second electrode 204and a second electrode of another pixel unit are formed in an openregion of the open-type mask, so as to form common electrode.

Thus it can be seen, the second portion 2042 of the second electrode 204manufactured in this way covers over whole upper surface of the firstportion 2041 of the second electrode 204 as well as of the pixeldefining layer 202.

Optionally, the step 405 may also comprise the following sub-steps of(not shown):

continuing to deposit, by means of slit-type fine metal mask, thematerial for the second electrode, to form a second portion of thesecond electrode; and

forming an elongated electrode on whole surface of the substrate 200with the material for the second electrode that has been deposited bymeans of slit-type fine metal mask. In other words, the second portionsof the second electrodes in each row of pixel unit form common electrodewhile leaving certain gaps among the second portions of the secondelectrodes in different rows of pixel units.

Thus it can be seen, the second portion of the second electrodemanufactured in this manner covers only over the upper surface of thefirst portion of the second electrode but over a portion of the uppersurface of the pixel defining layer.

With the abovementioned solutions, through two depositions of materialfor the electrode, the first portion and the second portion of thesecond electrode are formed in sequence. In a first deposition, thedeposited first portion of the second electrode is required to fill andlevel up difference in height between the pixel defining layer and thelight emitting layer, in other words, to substantially eliminatedifference in height between the pixel defining layer and the firstportion of the second electrode after the filling and leveling up. Then,a further deposition of the material for the electrode is performed toform the second portion of the second electrode, so that the secondportion of the second electrode is connected with a second electrode ofanother pixel unit, to form common electrode. In this way, the resultedcommon electrode substantially covers over the substrate in a planemanner, accordingly, phenomenon including fractures, abscissions,bubbles and the like due to existence of difference in height in thepixel region will be eliminated, averting adverse influence resulting infailures of the display apparatus.

A further description of objects, technique solutions and advantages ofthe present invention has been provided in conjunction withabovementioned embodiments. It should be understood that the abovedescription is merely used to illustrate specific embodiments of thepresent invention, but not to limit the present invention. All ofchanges, equivalent alternatives, improvements, made within principlesand spirit of the invention, should be included within the scope of thepresent invention.

What is claimed is:
 1. A method for manufacturing a first pixel unit,the method comprising: forming a first electrode; forming a pixeldefining layer, and patterning the pixel defining layer to define apixel region; forming a light emitting layer within the pixel region;forming a first portion of a second electrode on the light emittinglayer such that an upper surface of the first portion of the secondelectrode is substantially in same plane with an upper surface of thepixel defining layer; and forming then a second portion of the secondelectrode on the first portion of the second electrode, wherein thesecond portion of the second electrode is configured to be connectedwith a second electrode of a second pixel unit adjacent to the firstpixel unit.
 2. The method of claim 1, wherein the upper surface of thefirst portion of the second electrode is substantially in same planewith the upper surface of the pixel defining layer such that adifference in height between the first portion of the second electrodeand the pixel defining layer is from −200 nm to 200 nm.
 3. The method ofclaim 1, wherein the first portion of the second electrode is formed byusing a block-type fine metal mask.
 4. The method of claim 1, whereinthe second portion of the second electrode is formed by using aslit-type fine metal mask or an open-type mask.
 5. The method of claim2, wherein the second portion of the second electrode is formed by meansof using a slit-type fine metal mask or an open-type mask.
 6. The methodof claim 3, wherein the second portion of the second electrode is formedby means of using a slit-type fine metal mask or an open-type mask.
 7. Afirst pixel unit manufactured by the method of claim 1, the first pixelunit comprising: the first electrode; the pixel defining layer; thelight emitting layer; and the second electrode; wherein: the secondelectrode comprises the first portion and the second portion; the pixeldefining layer defines the pixel region; the light emitting layer andthe first portion of the second electrode are disposed successivelywithin the pixel region, and the upper surface of the first portion ofthe second electrode is substantially in same plane with the uppersurface of the pixel defining layer; and the second portion of thesecond electrode is positioned over the first portion and is configuredto be connected with a second electrode of a second pixel unit adjacentto the first pixel unit.
 8. The first pixel unit of claim 7, wherein theupper surface of the first portion of the second electrode issubstantially in same plane with the upper surface of the pixel defininglayer such that a difference in height between the first portion of thesecond electrode and the pixel defining layer is from −200 nm to 200 nm.9. The first pixel unit of claim 7, wherein the second portion of thesecond electrode is further formed on the pixel defining layer.
 10. Thefirst pixel unit of claim 9, wherein the second portion of the secondelectrode is further formed on a part of the pixel defining layer or theentire pixel defining layer.
 11. The first pixel unit of claim 7,wherein the first electrode is a positive electrode and the secondelectrode is a negative electrode.
 12. A display panel comprising thefirst pixel unit of claim
 7. 13. A display apparatus comprising thedisplay panel of claim
 12. 14. A display panel comprising the firstpixel unit of claim
 8. 15. A display apparatus comprising the displaypanel of claim
 14. 16. A display panel comprising the first pixel unitof claim
 10. 17. A display apparatus comprising the display panel ofclaim
 16. 18. A display panel comprising the first pixel unit of claim11.
 19. A display apparatus comprising the display panel of claim 18.